Work by Memcache

Memcached is a general-purpose distributed memory caching system that was originally developed by Danga Interactive for LiveJournal, but is now used by many other sites. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source (such as a database or API) must be read. Memcached runs on Unix, Windows and MacOS and is distributed under a permissive free software license. Memcached's APIs provide a giant hash table distributed across multiple machines. When the table is full, subsequent inserts cause older data to be purged in least recently used (LRU) order. Applications using Memcached typically layer requests and additions into core before falling back on a slower backing store, such as a database. The system is used by several very large, well-known sites including YouTube, Reddit, Zynga, Facebook and Twitter.

http://www.memcached.org/